Kredis
Kredis (Keyed Redis) encapsulates higher-level types and data structures around a single key, so you can interact with them as coherent objects rather than isolated procedural commands. These higher-level structures can be configured as attributes within Active Models and Active Records using a declarative DSL.
Kredis is configured using env-aware YAML files, using Rails.application.config_for, so you can locate the data structures on separate Redis instances, if you’ve reached a scale where a single shared instance is no longer sufficient.
Kredis provides namespacing support for keys such that you can safely run parallel testing against the data structures without different tests trampling each others data.
Examples
Kredis provides typed scalars for strings, integers, decimals, floats, booleans, datetimes, and JSON hashes:
string = Kredis.string "mystring" string.value = "hello world!" # => SET mystring "hello world" "hello world!" == string.value # => GET mystring integer = Kredis.integer "myinteger" integer.value = 5 # => SET myinteger "5" 5 == integer.value # => GET myinteger decimal = Kredis.decimal "mydecimal" # accuracy! decimal.value = "%.47f" % (1.0 / 10) # => SET mydecimal "0.10000000000000000555111512312578270211815834045" BigDecimal("0.10000000000000000555111512312578270211815834045e0") == decimal.value # => GET mydecimal float = Kredis.float "myfloat" # speed! float.value = 1.0 / 10 # => SET myfloat "0.1" 0.1 == float.value # => GET myfloat boolean = Kredis.boolean "myboolean" boolean.value = true # => SET myboolean "t" true == boolean.value # => GET myboolean datetime = Kredis.datetime "mydatetime" memoized_midnight = Time.zone.now.midnight datetime.value = memoized_midnight # SET mydatetime "2021-07-27T00:00:00.000000000Z" memoized_midnight == datetime.value # => GET mydatetime json = Kredis.json "myjson" json.value = { "one" => 1, "two" => "2" } # => SET myjson "{\"one\":1,\"two\":\"2\"}" { "one" => 1, "two" => "2" } == json.value # => GET myjson
There are data structures for counters, enums, flags, lists, unique lists, sets, and slots:
list = Kredis.list "mylist" list << "hello world!" # => RPUSH mylist "hello world!" [ "hello world!" ] == list.elements # => LRANGE mylist 0, -1 list.clear # => DEL mylist integer_list = Kredis.list "myintegerlist", typed: :integer, default: [ 1, 2, 3 ] # => EXISTS? myintegerlist, RPUSH myintegerlist "1" "2" "3" integer_list.append([ 4, 5, 6 ]) # => RPUSH myintegerlist "4" "5" "6" integer_list << 7 # => RPUSH myintegerlist "7" [ 1, 2, 3, 4, 5, 6, 7 ] == integer_list.elements # => LRANGE myintegerlist 0 -1 integer_list.clear # => DEL myintegerlist unique_list = Kredis.unique_list "myuniquelist" unique_list.append(%w[ 2 3 4 ]) # => LREM myuniquelist 0, "2" + LREM myuniquelist 0, "3" + LREM myuniquelist 0, "4" + RPUSH myuniquelist "2", "3", "4" unique_list.prepend(%w[ 1 2 3 4 ]) # => LREM myuniquelist 0, "1" + LREM myuniquelist 0, "2" + LREM myuniquelist 0, "3" + LREM myuniquelist 0, "4" + LPUSH myuniquelist "1", "2", "3", "4" unique_list.append([]) unique_list << "5" # => LREM myuniquelist 0, "5" + RPUSH myuniquelist "5" unique_list.remove(3) # => LREM myuniquelist 0, "3" [ "4", "2", "1", "5" ] == unique_list.elements # => LRANGE myuniquelist 0, -1 unique_list.clear # => DEL myuniquelist ordered_set = Kredis.ordered_set "myorderedset" ordered_set.append(%w[ 2 3 4 ]) # => ZADD myorderedset 1646131025.4953232 2 1646131025.495326 3 1646131025.4953272 4 ordered_set.prepend(%w[ 1 2 3 4 ]) # => ZADD myorderedset -1646131025.4957051 1 -1646131025.495707 2 -1646131025.4957082 3 -1646131025.4957092 4 ordered_set.append([]) ordered_set << "5" # => ZADD myorderedset 1646131025.4960442 5 ordered_set.remove(3) # => ZREM myorderedset 3 [ "4", "2", "1", "5" ] == ordered_set.elements # => ZRANGE myorderedset 0 -1 set = Kredis.set "myset", typed: :datetime set.add(DateTime.tomorrow, DateTime.yesterday) # => SADD myset "2021-02-03 00:00:00 +0100" "2021-02-01 00:00:00 +0100" set << DateTime.tomorrow # => SADD myset "2021-02-03 00:00:00 +0100" 2 == set.size # => SCARD myset [ DateTime.tomorrow, DateTime.yesterday ] == set.members # => SMEMBERS myset set.clear # => DEL myset hash = Kredis.hash "myhash" hash.update("key" => "value", "key2" => "value2") # => HSET myhash "key", "value", "key2", "value2" { "key" => "value", "key2" => "value2" } == hash.to_h # => HGETALL myhash "value2" == hash["key2"] # => HMGET myhash "key2" %w[ key key2 ] == hash.keys # => HKEYS myhash %w[ value value2 ] == hash.values # => HVALS myhash hash.remove # => DEL myhash high_scores = Kredis.hash "high_scores", typed: :integer high_scores.update(space_invaders: 100, pong: 42) # HSET high_scores "space_invaders", "100", "pong", "42" %w[ space_invaders pong ] == high_scores.keys # HKEYS high_scores [ 100, 42 ] == high_scores.values # HVALS high_scores { "space_invaders" => 100, "pong" => 42 } == high_scores.to_h # HGETALL high_scores head_count = Kredis.counter "headcount" 0 == head_count.value # => GET "headcount" head_count.increment # => SET headcount 0 NX + INCRBY headcount 1 head_count.increment # => SET headcount 0 NX + INCRBY headcount 1 head_count.decrement # => SET headcount 0 NX + DECRBY headcount 1 1 == head_count.value # => GET "headcount" counter = Kredis.counter "mycounter", expires_in: 5.seconds counter.increment by: 2 # => SET mycounter 0 EX 5 NX + INCRBY "mycounter" 2 2 == counter.value # => GET "mycounter" sleep 6.seconds 0 == counter.value # => GET "mycounter" counter.reset # => DEL mycounter cycle = Kredis.cycle "mycycle", values: %i[ one two three ] :one == cycle.value # => GET mycycle cycle.next # => GET mycycle + SET mycycle 1 :two == cycle.value # => GET mycycle cycle.next # => GET mycycle + SET mycycle 2 :three == cycle.value # => GET mycycle cycle.next # => GET mycycle + SET mycycle 0 :one == cycle.value # => GET mycycle cycle.reset # => DEL mycycle enum = Kredis.enum "myenum", values: %w[ one two three ], default: "one" "one" == enum.value # => GET myenum true == enum.one? # => GET myenum enum.value = "two" # => SET myenum "two" "two" == enum.value # => GET myenum enum.three! # => SET myenum "three" "three" == enum.value # => GET myenum enum.value = "four" "three" == enum.value # => GET myenum enum.reset # => DEL myenum "one" == enum.value # => GET myenum slots = Kredis.slots "myslots", available: 3 true == slots.available? # => GET myslots slots.reserve # => INCR myslots true == slots.available? # => GET myslots slots.reserve # => INCR myslots true == slots.available? # => GET myslots slots.reserve # => INCR myslots false == slots.available? # => GET myslots slots.reserve # => INCR myslots + DECR myslots false == slots.available? # => GET myslots slots.release # => DECR myslots true == slots.available? # => GET myslots slots.reset # => DEL myslots slot = Kredis.slot "myslot" true == slot.available? # => GET myslot slot.reserve # => INCR myslot false == slot.available? # => GET myslot slot.release # => DECR myslot true == slot.available? # => GET myslot slot.reset # => DEL myslot flag = Kredis.flag "myflag" false == flag.marked? # => EXISTS myflag flag.mark # => SET myflag 1 true == flag.marked? # => EXISTS myflag flag.remove # => DEL myflag false == flag.marked? # => EXISTS myflag true == flag.mark(expires_in: 1.second, force: false) #=> SET myflag 1 EX 1 NX false == flag.mark(expires_in: 10.seconds, force: false) #=> SET myflag 10 EX 1 NX true == flag.marked? #=> EXISTS myflag sleep 0.5.seconds true == flag.marked? #=> EXISTS myflag sleep 0.6.seconds false == flag.marked? #=> EXISTS myflag limiter = Kredis.limiter "mylimit", limit: 3, expires_in: 5.seconds 0 == limiter.value # => GET "limiter" limiter.poke # => SET limiter 0 NX + INCRBY limiter 1 limiter.poke # => SET limiter 0 NX + INCRBY limiter 1 false == limiter.exceeded? # => GET "limiter" limiter.poke # => SET limiter 0 NX + INCRBY limiter 1 true == limiter.exceeded? # => GET "limiter" sleep 6 limiter.poke # => SET limiter 0 NX + INCRBY limiter 1 limiter.poke # => SET limiter 0 NX + INCRBY limiter 1 false == limiter.exceeded? # => GET "limiter"
Models
You can use all these structures in models:
class Person < ApplicationRecord kredis_list :names kredis_list :names_with_custom_key_via_lambda, key: ->(p) { "person:#{p.id}:names_customized" } kredis_list :names_with_custom_key_via_method, key: :generate_names_key kredis_unique_list :skills, limit: 2 kredis_enum :morning, values: %w[ bright blue black ], default: "bright" kredis_counter :steps, expires_in: 1.hour private def generate_names_key "key-generated-from-private-method" end end person = Person.find(5) person.names.append "David", "Heinemeier", "Hansson" # => RPUSH people:5:names "David" "Heinemeier" "Hansson" true == person.morning.bright? # => GET people:5:morning person.morning.value = "blue" # => SET people:5:morning true == person.morning.blue? # => GET people:5:morning
Default values
You can set a default value for all types. For example:
list = Kredis.list "favorite_colors", default: [ "red", "green", "blue" ] # or, in a model class Person < ApplicationRecord kredis_string :name, default: "Unknown" kredis_list :favorite_colors, default: [ "red", "green", "blue" ] end
There’s a performance overhead to consider though. When you first read or write an attribute in a model, Kredis will
check if the underlying Redis key exists, while watching for concurrent changes, and if it does not,
write the specified default value.
This means that using default values in a typical Rails app additional Redis calls (WATCH, EXISTS, UNWATCH) will be
executed for each Kredis attribute with a default value read or written during a request.
Callbacks
You can also define after_change callbacks that trigger on mutations:
class Person < ApplicationRecord kredis_list :names, after_change: ->(p) { } kredis_unique_list :skills, limit: 2, after_change: :skillset_changed def skillset_changed end end
Multiple Redis servers
And using structures on a different than the default shared redis instance, relying on config/redis/secondary.yml:
one_string = Kredis.string "mystring" two_string = Kredis.string "mystring", config: :secondary one_string.value = "just on shared" two_string.value != one_string.value
Installation
- Run
./bin/bundle add kredis - Run
./bin/rails kredis:installto add a default configuration atconfig/redis/shared.yml
Additional configurations can be added under config/redis/*.yml and referenced when a type is created. For example, Kredis.string("mystring", config: :strings) would lookup config/redis/strings.yml.
Kredis passes the configuration to Redis.new to establish the connection. See the Redis documentation for other configuration options.
If you don’t have config/redis/shared.yml (or use another named configuration), Kredis will default to look in env for REDIS_URL, then fallback to a default URL of redis://127.0.0.1:6379/0.
Redis support
Kredis works with Redis server 4.0+, with the Redis Ruby client version 4.2+. Redis Cluster is not supported.
Setting SSL options on Redis Connections
If you need to connect to Redis with SSL, the recommended approach is to set your Redis instance manually by adding an entry to the Kredis::Connections.connections hash. Below an example showing how to connect to Redis using Client Authentication:
Kredis::Connections.connections[:shared] = Redis.new( url: ENV["REDIS_URL"], ssl_params: { cert_store: OpenSSL::X509::Store.new.tap { |store| store.add_file(Rails.root.join("config", "ca_cert.pem").to_s) }, cert: OpenSSL::X509::Certificate.new(File.read( Rails.root.join("config", "client.crt") )), key: OpenSSL::PKey::RSA.new( Rails.application.credentials.redis[:client_key] ), verify_mode: OpenSSL::SSL::VERIFY_PEER } )
The above code could be added to either config/environments/production.rb or an initializer. Please ensure that your client private key, if used, is stored your credentials file or another secure location.
Configure how the redis client is created
You can configure how the redis client is created by setting config.kredis.connector in your application.rb:
config.kredis.connector = ->(config) { SomeRedisProxy.new(config) }
By default Kredis will use Redis.new(config).
Development
A development console is available by running bin/console.
From there, you can experiment with Kredis. e.g.
>> str = Kredis.string "mystring" Kredis (0.1ms) Connected to shared => #> str.value = "hello, world" Kredis Proxy (2.4ms) SET mystring ["hello, world"] => "hello, world" >> str.value
Run tests with bin/test.
debug can be used in the development console and in the test suite by inserting a
breakpoint, e.g. debugger.
License
Kredis is released under the MIT License.